The parents, who were already working with police, did as they were told.

Mueller was reported missing a day earlier. The Scottsdale Community College student was last seen around 9:30 p.m. after finishing his shift at a gas station at Miller and McDowell roads.

At the pay phone, Larry found Mueller's driver's license and a note that looked like his son's handwriting. There were specific instructions that included a request for thousands of dollars, a drop-off point and a threat that Mueller would be killed.

The family delivered the money, but it was not picked up. Three separate ransom calls and money drops followed those first two months, and the money wasn't taken. Mueller's vehicle was later found at Phoenix Sky Harbor International Airport.

Earlier this year, Lockerby was looking at a 2007 case where a bone had been found in north Scottsdale near a popular hiking spot.

The Department of Public Safety crime lab created a DNA bone profile. A forensic scientist determined the femur was from a White man in his 20s, about 5 feet 8 inches tall, that had been in the desert for up to five years.

The ages didn't match. By 2007, Mueller would have been 49; this bone was from a man in his 20s.

Lockerby contacted Mueller's brothers, who told him their parents were still alive. In July, a DNA profile created with a combination of Larry and Beverly's DNA was run through a federal database. It matched the bone's profile. After the DNA hit, Lockerby called the forensic scientist.

"She said there's no way this bone has been in the elements for 30 years," Lockerby said. "That leads us to believe the bone was dug up within the last one to five years. It's been in some sort of burial site."

The case has been reclassified as a homicide, and Lockerby is planning another search for Mueller's remains. He will also contact people interviewed in 1977.

At the time, friends believed Mueller was possibly involved in a marijuana deal.

"Maybe (Mueller) got involved in something else, but there was nothing glaring in his background," Lockerby said. "This was a stand-up kid with his whole life in front of him."